1. Field of the Invention
This invention relates to a driven rotary body rotating due to pressurized contact with a conveyance rotary body and driven by this conveyance rotary body and, e.g., to a pinch roller in pressurized contact with a conveyance roller as a driven rotary body, a sheet material conveying apparatus having the pinch roller, and a recording apparatus having the sheet material conveying apparatus.
2. Description of Related Background Art
In apparatuses such as printers, photocopiers, and facsimile machines, sheet materials stacked on a sheet material stacking section are separately fed sheet by sheet to effect recording on the sheet materials or to read original documents, and after the front ends of the sheet materials separated at the sheet material conveying section are aligned, the sheet materials are conveyed to a recording reading area.
FIG. 5 is a perspective view showing a conveyance portion of a conventional conveying apparatus; FIG. 6 is a structural cross-sectional view for illustrating a structure of a sheet material conveyance portion of the conventional conveying apparatus.
The sheet material separately conveyed from a feeding apparatus (not shown) is so aligned as to arrange the front end thereof at a conveyance portion 110 with a conveyance roller 111 and a pinch roller 104 in pressure contact with the conveyance roller 111.
The sheet material with the aligned front end is transmitted to a recording portion 130 by the conveyance roller 111, and a recording head 132 records where the sheet material is supported at a platen 131.
The recorded sheet material is delivered to the exterior of the apparatus through a delivery portion 140 formed of at least one delivery roller 141 and corresponding delivery spur 142.
The conveyance roller 111 is a metal roller having a sheet material conveyance surface on which ground particles are coated, and the pinch roller 104 is formed of a molded resin such as POM (polyoxymethylene).
The pinch roller 104 has a hole opened in a longitudinal direction, is supported by a pinch roller holder 102 attached rotatably to a body chassis 101 where a metal shaft 105 is penetrated through the hole, and is in pressure contact with the conveyance roller 111 by a pinch roller spring 103.
FIG. 7 shows a shape of the pinch roller 104 in the conventional apparatus as described above.
The pinch roller 104, in which the hole is opened as to receive the metal shaft as shown in FIG. 7(a), is formed by parting the mold around one end of the roller in the longitudinal direction as shown in FIG. 7(b). That is, as shown in FIG. 7(b), the pinch roller 104 is molded in a shape as shown in FIG. 7(a) with molds 151, 152 respectively extending in the longitudinal direction and being parted at a partition line PL around the one end of the roller in the longitudinal direction.
A surface of the pinch roller 104 is necessarily to be molded with as few scratches as possible to prevent damage from occurring on the sheet material, and the diameter of the center portion is necessarily larger than each end to prevent scratching the sheet material by opposite ends of the pinch roller in the longitudinal direction. That is, where the pinch roller diameters at positions (1), (2), (3) in FIG. 7(a) are φA±a, φB±b, and φC±c, the relation among those diameters is B−b>A+a, and A=C. As shown in FIG. 7(a), length D of the conventional pinch roller 104 in the longitudinal direction is about 20 mm.
To the contrary, in a case where the metal shaft is eliminated for cost reduction, where the pinch roller is molded as an integral body to reduce the unit price, and where the length of each roller is made longer to reduce the number of the pinch rollers, the length of the mold for molding the roller may become longer in a longitudinal direction by an extended portion of the roller with a molding method in which the molds are parted at one side in the longitudinal direction of the roller in substantially the same way as in the conventional method.
Therefore, problems arise not only in that the production of the mold becomes difficult, but also in that the molding cycle for the roller becomes longer due to cooling of the mold, that accurate sizes tend not to be obtained during molding, and that defects tend to occur, and consequently, the advantages of the cost reduction may be nullified.
If the above problems could be solved by using particular resin materials, the valuable advantages of cost reduction may not be adequately achieved due to costs and availability of the materials or the like.